Also, a lot of sites use email where they could (should?) be providing RSS, for updates and news stuff. So to see those in the same place as RSS feeds, either you use a common client for both, or convert one into the other.
Feedbin seems to permit receiving email newsletters as a feed, so that's one of the few making email into RSS, whereas the others all turn RSS into email.
Feedbin seems to permit receiving email newsletters as a feed, so that's one of the few making email into RSS, whereas the others all turn RSS into email.